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Fast integer least-squares estimation for GNSS high-dimensional ambiguity resolution using lattice theory / S. Jazaeri in Journal of geodesy, vol 86 n° 2 (February 2012)  

Public [article]  inJournal of geodesy > vol 86 n° 2 (February 2012) . - pp 123 - 137 Titre : Fast integer least-squares estimation for GNSS high-dimensional ambiguity resolution using lattice theory Type de document : Article/Communication Auteurs : S. Jazaeri, Auteur ; Ali Reza Amiri-Simkooei, Auteur ; M. Sharifi, Auteur Année de publication : 2012 Article en page(s) : pp 123 - 137 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] analyse comparative [Termes IGN] données GNSS [Termes IGN] méthode des moindres carrés [Termes IGN] résolution d'ambiguïté Résumé : (Auteur) GNSS ambiguity resolution is the key issue in the high-precision relative geodetic positioning and navigation applications. It is a problem of integer programming plus integer quality evaluation. Different integer search estimation methods have been proposed for the integer solution of ambiguity resolution. Slow rate of convergence is the main obstacle to the existing methods where tens of ambiguities are involved. Herein, integer search estimation for the GNSS ambiguity resolution based on the lattice theory is proposed. It is mathematically shown that the closest lattice point problem is the same as the integer least-squares (ILS) estimation problem and that the lattice reduction speeds up searching process. We have implemented three integer search strategies: Agrell, Eriksson, Vardy, Zeger (AEVZ), modification of Schnorr–Euchner enumeration (M-SE) and modification of Viterbo-Boutros enumeration (M-VB). The methods have been numerically implemented in several simulated examples under different scenarios and over 100 independent runs. The decorrelation process (or unimodular transformations) has been first used to transform the original ILS problem to a new one in all simulations. We have then applied different search algorithms to the transformed ILS problem. The numerical simulations have shown that AEVZ, M-SE, and M-VB are about 320, 120 and 50 times faster than LAMBDA, respectively, for a search space of dimension 40. This number could change to about 350, 160 and 60 for dimension 45. The AEVZ is shown to be faster than MLAMBDA by a factor of 5. Similar conclusions could be made using the application of the proposed algorithms to the real GPS data. Numéro de notice : A2012-142 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0501-z Date de publication en ligne : 30/07/2011 En ligne : https://doi.org/10.1007/s00190-011-0501-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31589 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2012021	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Ray-traced slant factors for mitigating the tropospheric delay at the observation level / L. Urquhart in Journal of geodesy, vol 86 n° 2 (February 2012)  

Public [article]  inJournal of geodesy > vol 86 n° 2 (February 2012) . - pp 149 - 160 Titre : Ray-traced slant factors for mitigating the tropospheric delay at the observation level Type de document : Article/Communication Auteurs : L. Urquhart, Auteur ; F. Nievinski, Auteur ; Marcelo C. Santos, Auteur Année de publication : 2012 Article en page(s) : pp 149 - 160 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] gradient de pente [Termes IGN] lancer de rayons [Termes IGN] modèle météorologique [Termes IGN] positionnement ponctuel précis [Termes IGN] propagation troposphérique [Termes IGN] signal GPS Résumé : (Auteur) Three-dimensional ray tracing through a numerical weather model has been applied to a global precise point positioning (PPP) campaign for modeling both the elevation angle- and azimuth-dependence of the tropospheric delay. Rather than applying the ray-traced slant delays directly, the delay has been parameterized in terms of slant factors, which are applied in a similar manner to traditional mapping functions, but which can account for the azimuthal asymmetry of the delay. Five strategies are considered: (1) Vienna Mapping Functions 1 (VMF1) and estimation of a residual zenith delay parameter; (2) VMF1, estimation of a residual zenith delay and estimation of two tropospheric gradient parameters; (3) three-dimensional ray-traced slant factors and estimation of a residual zenith delay; (4) using only ray-traced slant factors and no estimation of any tropospheric parameters and; (5) using both ray-traced slant factors and estimating a residual zenith delay and two tropospheric gradient parameters. The use of the ray-traced slant factors (solution 3) showed a 3.8% improvement in the repeatability of the up component when compared to the assumption of a symmetric atmosphere (solution 1), while the estimation of two tropospheric gradient parameters gave the best results showing an 7.6% improvement over solution 1 in the up component. Solution 4 performed well in the horizontal domain, allowing for sub-centimeter repeatability but the up component was degraded due to deficiencies in the modeling of the zenith delay, particularly for stations located at equatorial latitudes. The magnitude of the differences in the mean coordinates between solution 2 and solution 3, and the strong correlation with the differences between the north component and the ray-traced gradients (coefficient of correlation of 0.83), as well as the impact of observation geometry on the gradient solution indicate that the use of the ray-traced slant factors could have an implication on the realization of reference frames. The estimated tropospheric products from the PPP solutions were compared to those derived from ray tracing. For the zenith delay, a root mean square (RMS) of 5.4 mm was found, while for the gradient terms, a correlation coefficient of 0.46 for the N–S and 0.42 for the E–W was found for the north–south and east–west components, suggesting that there are still important differences in the gradient parameters which could be due to either errors in the NWM or to non-tropospheric error sources leaking into the PPP-estimated gradients. Numéro de notice : A2012-143 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0503-x Date de publication en ligne : 04/09/2011 En ligne : https://doi.org/10.1007/s00190-011-0503-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31590 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2012021	RAB	Revue	Centre de documentation	En réserve L003	Disponible